Circuit breaker having cam controlled contact bar



Jan' 23, 1962 w. H` MIDDENDORF 3,018,351

CIRCUIT BREAKER HAVING CAM CONTROLLED CONTACT BAR Filed July 24, 1958 5 Sheets-Sheet 1 es 5g AT TOENE )'5.

3,018,351 CIRCUIT BREAKER HAVING CAM CONTROLLED CONTACT BAR Filed July 24, 195e Jan. 23, 1962 w. H, MIDDENDORF 3 Sheets-Sheet 2 ATTONEYS.

Jan. 23, 1962 w. H. MIDDENDORF 3,018,351

CIRCUIT BREAKER HAVING CAM CONTROLLED CONTACT BAR Filed July 24. 1958 5 Sheets-Sheet 3 n-r ron/evs.

CIRCUIT BREAKER HAVING CAM CNTROLLED CONTACT BAR William H. Middendorf, Covington, Ky., assignor to The Wadsworth Electric Manufacturing Company, Inc., Covington, Ky., a corporation of Kentucky Filed July 24, 1958, Ser. No. 750,612 15 Claims. (Cl. 200-116) This invention relates toan electrical circuit breaker and is directed particularly to an inexpensive breaker manufacturable from comparatively few parts, the breaker having the characteristics of quick make and break operation, as well as a common trip mechanism for multipole operation.

The circuit breaker of the present invention comprises a generally horizontal contact bar having a movable contact at one end cooperating with a fixed contact, and a latching surface at the other end cooperating with a latch movable in response to overload current. The bar has an integral transverse pivot pin guided by a cam recess in the sides of the breaker. Movement of the bar to its several positions is effected in part by a spring acting on the bar and in part by a generally vertical handle pivoted above the contact bar and having a lower extremity engaging the pivot pin.

It has been an objective of the invention to provide a circuit breaker utilizing a minimum of moving parts, namely an operating handle, ay contact bar associated therewith, single spring means biasing said contact bar for both make and break and a current responsive latch.

It has been another objective of the invention to provide such a circuit breaker in which the component parts cooperate to provide snap action of the contacts in both the make and break operations utilizing a single spring means as the motive force for the snap action in both operations.

It has been another objective of the invention to provide a circuit breaker as described above in which spring means normally biases the contact bar toward a fixed co-ntact. The snap action during the make operation is provided by causing the lower extremity of the operating handleY to ride over the contact bar pivot pin forcing the pin and bar downwardly against the action of the spring. The thereby stressed spring snaps the contact bar upwardly toward the fixed contact when the lower extremity of the operating handle passes -beyond the contact bar pivot pin. The cam surface which guides the movement of the pivot pin cooperates with the shape of the lower extremity of the operating handle to provide assurance that the operating handle Will be out of the way of the contact bar and its pivot pin when the contact bar is snapped upwardly.

It has been another objective of the invention to provide a circuit lbreaker as described above in which the spring acts on said contact bar at a point intermediate the pivot pin and the latching surface so that on make the latching surface engages the' latch to form a pivot about which the contact bar swings into contact with the fixed contact; and on break, the pivot pin forms a fulcrum about which the contact bar swings to separate the contacts.

It has been another -objective of the invention to provide a circuit breaker of the type described above in which the cam surface engaged by the pivot pin during the make operation is generally an arc of a circle of a radius equal to the distance between the latching surface and the pivot pin, the circle having the latch as a center whereby engagement of the latching surface with the latch will be effected regardless of the particular position of the pivot pin on the cam surface.

It has been another objective of the invention to pro- United States Patent O 3,018,351 Patented Jan. 23, 1962 "ice vide a circuit 'breaker as described in the preceding paragraph in which a bar stop surface is fixed in the housing and engageable by the contact end of the contact bar to form a pivot about which the contact bar swings during the first portion of the make operation to swing the latch ing surface into engagement with the latch,A the Contact bar pivot pin riding on the cam surface to` guide the latching surface into engagement with the latch.

It has been another objective of the invention to provide a circuit breaker having a contact bar which, on break, swings its contact'away from ya fixedl contact in such a manner as initially to cause the movable contact to pivot on the fixed contact thereby breaking any previously formed weld, corrosion or the like whichmight tend to cause the contact tobe fixed together. The pivoting action is accomplished by the shape of the carri surface engaged by the contact bar pivot pin, which cam surface permits the pivot pin, on tbreakf initially to slide so that the bar pivots about the fixed contact; and subsequently to substantially block movement o'f the pivot pin so that the contact bar swings about the pivot pin to complete the sepa-ration of the contacts.

It has been another objective to provide a circuit breaker in which the manual operating means acts di'- rectly upon the bar carrying the movable contact to provide positive opening of the circuit in case of an emergency.

it has been another objective of the invention to so connect the single spring means between the contact bar and the operating handle so that the operating handle will be urged into three positions corresponding to the three positions of the contact bar, namely made position, tripped position and intermediate position prior to making after the breaker has 'been tripped, thereby indicating the condition of the contact bar.

It has been another objective of the invention to provide a pair of circuit breakers of the type described above disposed in side'by side relationship and having a common trip member engageable by a tripped contact bar of one of the pair to move the common trip member into engagement with the pivot pin of the other of the pair to cause its release from its associated latchwithout engagement of the latch itself.

It has been another objective of the invention to provide a circuit breaker having a current-responsive latch member and a contact bar having a latch portion c ooperating with the current-responsive latch member, the current-responsive latch member being movable in a first direction for unlatching and the contact bar being `movable in the opposite direction either by a manuallyoperable handle or by a common trip member for multi; pole operation to effect unlatching. This objective of the invention represents ka departure from the prior art practices in circuitV breakers of the oatingdb'ar vtype for in the prior art it has been the practice to effect manual opening of the contacts by depressing the contact bar away from the fixed contact.

By the present construction, quick, snap action break can be effected manually. Further, the particular design including the movement of the contact 'bar lin a direction opposite to movement of the current responsive latch member, makes possible economy in the thickness dimension of the circuit breaker and simplification of the common trip mechanism for multi-pole operation.

lt has been another objective of the invention to provide a circuit breaker housing of a minimum number of parts, all of which being easy to manufacture and as# semble.

It has been another objective of the invention to provide a circuit breaker of the type described above which can be tripped manually without engagement of the latch member.

It hasl been another objective of the invention to provide a circuit breaker which is adaptable for use in standard bus bar arrangements.

These and other objectives of the invention will become more readily apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. l is 'a sectional view partly in elevation of a circuit breaker constructed in accordance with this invention with parts shown in tripped position;

FIG. 2 is va view similar to FIG. l showing the parts in intermediate or reset position;

FIG. 3 is a view similar to FIG. 1 showing parts in circuit closed or made position;

IFIG. 4 is a top plan view of the circuit breaker;

FIG. 5 is -a cross-sectional view taken along Alines 5-5 of FIG. 3;

FIG. 6 is a cross-sectional view taken along lines 6--6 of FIG. 3;

FIG. 7is a cross-sectional view taken along lines 7--7 of FIG. 3;

FIGS. 8-16 are diagrammatic views showing the rela tionship of the parts during the various phases of operation;

FIG. 17 is an elevational view partly in section of a pair of circuit breakers sh-owing a common tripping means;

FIG. 18 is a diagrammatic side elevational view of the circuit breaker showing a common tripping means;

FIG. 19 is a perspective view showing a common trip element; an-d FIG. 20 is a cross sectional view similar to FIG. 6 showing an alternative form of the invention.

The principal elements of the invention and their relative positions are best illustrated in FIGS. 1-3. The elements are for the most part contained within a housing 20 .-having an `end wall 22 on the latching side of the breaker, the end wall 22 being internally recessed at 24 to provide space for movement of a contact bar 25 and a shoulder 26 to form an abutment for the contact bar. A lower external recess 28 is provided to cooperate with a mounting member in a standard bus bar arrangement with whichvthe present invention is useful.

An upper recess 29 is provided to receive a standard line terminal connector 30 for connecting the breaker in its circuit.

The housing 20 has an end wall 32 through which terminals 34 project, the terminals being designed to embrace a blade on a bus bar to form an electrical connec- 4tion therewith. A top wall 36 has an opening 38 through which an operating handle 40 project-s, the opening 38 being in part delined by surfaces 42 and 44 which confine the movement of the operating handle 40 within operating limits. The lower edge 46 of the opening 38 is arcuately formed to cooperate with an arcuate shoulder 48 on the operating handle so as to complete the encasement of electrical components of the circuit breaker in all positions of the operating handle. The top wall 36 has another opening 50 through which an adjusting screw 52 passes and is sealed in position by plug 53. The screw engages an abutment 54 which is integral with the housing 20. The screw is threaded into -a strap 56 electrically connected to the connector 30. A thermally responsive bimetallic element 58 is electrically as well as mechanically lixed at 60 to the strap 56.

It can be seen by rotating compensating screw 52 the upper portion of the strap 56 can be raised and lowered causing the bimetal to swing toward and away from the contact bar 25 in order to set the precise point at which overloadfcurrent will cause the bimetal to move out of engagement with the contact bar.

The housing is completed by a bottom wall 61 having an upwardly projectinginclined bar stop surface 62 and side walls 63 and 64. The side walls 63 and 64 are provided with recesses 66 which are mirror imagesof each other and include cam surfaces 66a, 66b, and`66c whic receive a pivot' pin 68 xed in the contact bar 25. The cam recesses 66 guide the movement of the pivot pin as the contact bar 25 is urged to its several positions. As viewed in FIG. l, the right end of contact bar 25 is, in plan, an L-shaped hook having a projection 69 (best shown in FIG. 6) forming a latch engaging surface which cooperates with the lower edge 70 of a latch 71 xed on the Ibimetallic element 58. The latch 71 isl swingab-le between latching and unlatching positions depending upon the overload current passing through the bimetal 58 to which the latch 71 is attached. The latch element 71 may also or alternatively be urged `to unlatching position through the use of a magnetic circuit of the type described in Patent No. 2,716,679 and for this purpose the latch 71 may be constructed of ferro-magnetic material. While the illustrated latch mechanism is preferred, the direc-,M tions of movement of the current responsive member and i' the projection 69,y and their positions, may be reversed without materially affecting the operation of the breaker.

The recess cam surface 66a is arcuate to cooperate with latching surface 69 and the latch edge 70 for assurance of latching with every operation of the circuit breaker. To this end the surface 66a isthe arc of a circle whose radius is the distance between the point of engagement of pin 68 with surface 66a and the point of engagement of latching surface 69 and the latch edge 70, the center of the circle being the latch edge 70. Thus, regardless of the position of the pin 68 on the surface 66a, 4the latching surface 69 can be swung into latching engagement with the latch edge 70 of the latch 71.

The left end of contact bar 25 is provided with a contact 72 which cooperates with a fixed contact 73 mechanically supported by a strap 74 which electrically connects the fixed contact 73 to the terminals 34.

A pig tail 75 is connected at 76 to the contact bar and at 59 to the bimetal to form electrical connection between the contact 4bar and the bimetal. The load current flows through the path constituted by terminals 34, strap 74, contacts 72 and 73, the contact bar 25, pi-g tail 75, bimetal 58, strap 56 -and terminal connector 30.

The contact bar 25 is manipulated by the handle 40 pivoted at 77 to the housing sides 63 and 64. The handle has a bifurcated lower extremity 78 which straddles the contact bar and has surfaces 79 and 80 engageable with pin 68 for the manipulation of the contact bar.

It should be understood that instead of the bifurca-ted handle straddling the contact bar, the contact bar could be :slotted to expose the pin 68 intermediate the ends of the slots, the operating handle having a single lower extremity extending into the slot for engagement with the pin 68. Such a structure is illustrated in FIG. 20.

A tension spring 81 is connected between a pin 82 on the lower extremity 78 on the handle 40 and to a transverse member 83 integral with the contact bar 25 to urge the contact bar bodily upward. The member 83 to which the spring is connected is located between the pivot pin 68 and the latching -surface 69 so that the single spring can pivot the contact bar either clockwise about latching surface 70 to bring the contacts 72 and 73 into engagement or counter-clockwise about pivot pin 68 to snap the cotnact out of engagement.

It should be understood that if the slotted contact bar cooperating with an' operating handle has a single leg projecting through the Contact bar, it would be advisable to use two springs, one disposed on either side of the operating handle in order tobalance the contact bar and operating handle against twisting movement. In this construction, the two springs would constitute the single spring means which acts on the contact bar in view of the fact that the spring perform identical functions.

OPERATION FIG. 1 illustrates the disposition of the elements of the circuit breaker after it has been tripped by the 'shifting of the latch 71 due 'to a Vcurrent overload, this being tripped position. In this position, the spring 81 urges the contact bar 25 upwardly, upward movement of the bar being restrained by the abutment 26 in the housing and the cam surface 66b.

Prior to closing the contacts, the operating handle must be shifted so that its lower extremity is on the right side of pivot pin 68 as sh'own in FIG. 2, this being the reset position.` The intermediate positions that the elements occupy during the transition from trippedy position to reset position are illustrated in FIGS. 1l to 13, the arrows indicating the direction of force applied to the contact bar 25. In the first stage shown in FIG. 1l, the contact bar is forced down and to the right under the control of the handle surface 79 acting on pin 68, and the recess surface 66e confining the movement of the pivot pin 68.

In FIG. 12, the breaker is in an unstable position in which the contact pin is a-t the apex formed between handle surfaces 79 and 80. In FIG. 13, also FIG. 2, the pivot pin 68 is shifted over to the left side of the operating handle with the parts in reset position.

FIG. 3 illustrates a disposition of the operating elements when the breaker is in closed position. The sequence of positions of the elements as the breaker is shifted to the closed position of FIG. 3 is illustrated in FIGS. 14 to 16. The handle is moved clockwise so that surface 8i) of Vthe handle bears against the pivot pin 68 sliding 'the contact bar 25 toward the left and down, the movements being guided first by the recess surface 66h acting on the pivot pin 68 and second by the inclined cam surface 62 acting on the left end of the contact bar. During lthis stage there is a slight pivoting of the contact bar clockwise about the left end of the contact bar. In the next stage illustrated in FIG. 15, the pivot pin 68 moves down guided by recess surface 66a, the contact bar continuing to pivot clockwise about the point of engagement of the left end of the contact bar with the cam stop surface 62. Because the surface 66a is the arc of a circle having its center at latching edge 7 t) and because the distance between the point of engagement of pin 68 with surface 66a and the contact bar latching surface 69 is a radius of that circle, when the right end of the contact bar 2S has been pivoted beyond the latching edge 70 as illustrated in FIG. 15, the latching surface is in a position to engage the latch regardless of the position of the pivot pin on the surface 66a. This is important to insure closing of the breaker during every operation even though a more rapid movement of the handle during the closing operation might cause the pivot pin to move downwardly on surface 66a farther than with slower more deliberate movements of the operating handle.

In FIG. 15, the contact bar is in an unstable position at the apex between handle surfaces 79 and 80. Asthe handle swings past the pivot pin 68 as illustrated in FIG. 16, the spring snaps the contact bar bodily upward until vthe la'tching surface engages the latch edge 70. Thereafter, the contact bar pivots about its point of latching engagement to snap the contacts closed to the position shown in FIG. 3, also shown in FIG. 8.

Manual trp From the position of FIG. 3, the circuit breaker can be manually tripped, the sequence of positions being illustrated in FIGS. 8 to l0. For manual tripping the operating handle is rotated counter-clockwise causing the surface 79 to bear against pin 68 to shift the Contact bar toward the right thereby bringing the latching surface 69 out of engagement with the latch edge 70. Thereafter, the contact bar swings counter-clockwise about the point of engagement of pivot pin 68 with recess surface 66h. In so pivoting, the contact bar attains the position shown in FIG. 1 as Well as FIG. 10.

6 Aufman'c tripping Automatic tripping causes movement of the latch 71 in response to overload current similar in most respects to manual tripping and reference may be had to FIGS. 8 to 10. However, one important distinction should be noted in manual tripping. In manual tripping, the contact bar is shifted bodily toward the right and, depending upon the pressure applied manually to the operating handle, the relative position of the parts is variable. In automatic tripping the contact bar remains stationary while the latch edge 70 moves out of the way of the latching surface '69. Immediately after disengagement of the latching surface with the latch, the contact bar begins to pivot about the point of engagement of contact 72 with contact 73, the pin 68 sliding upwardly along recess surface 66a. When the pin 68 reaches the apex formed by surfaces 66a and 66b, the contact bar rotates counter-clockwise about the point of engagement, pin 68 with surface 66h.

The initial pivoting of the contact bar about its contacts brings a considerable force to bear against any corroding or welding which might tend to cause the contacts to adhere to each other rather than to make a fast break.

HANDLE POSITIONS The three positions of equilibrium of the breaker are illustrated in FIGS. l, 2 and 3. In each of these positions, the handle is maintained in a fixed position by the spring 81 which serves to indicate visually the condition ofthe circuit breaker. In FIG. 1, the spring biases the handle in a counter-clockwise direction in which the su'rface 79 thereof bears against pin 68 indicatingA that lthe circuit breaker has been tripped. In FIG. 2, the upper portion of the handle bears against the lwer edge 42 of the opening 38, the handle being biased counter-clockwise to this position by the spring 81. y

In FIG. 3, the spring biases the handle in a clockwise direction so that surface 79 bears against pivot pin 68. The position of the handle in FIG. 3 differs from that in FIG. 1 in that the pivot pin 68 bears against recess sur- -lface 66C in FIG. 1, whereas in FIG. 3 the pivot pin has been shifted to the left bearing against recess surface 66a. As a consequence, the counter-clockwise position of the handle in the closed position of FIG. 3 is farther to the right than in the tripped position of FIG. 1.

ACOMMON TRI-P FOR MULTI-POLE OPERATION FIGS. 17 to 19 illustrated an' arrangement by which the tripping of either one of a pair of circuit breakers will cause the tripping of an adjacent one.

FIG. 17 shows two identical circuit breakers 84 and 8S of the type described above disposed in side by side relation. The operating of the circuit breakers is interlocked by a com-mon trip member 86 pivotally mounted at S7 to breaker 85. The pivot pin 68 projects through a hole 88 which is simply an extension ofthe cam recess 66. The outward extremity of the pin 68 is engageable by a. flange portion 89 on the triangular surface 90 of the common trip member 86. A second flange portion 91 is integral with the other side of the triangular portion 90. A pin 92, integral with the common trip member, projects through arcuate slots 9?; on adjacent side walls of the breakers and is engageable bythe contact bar y25 of either breaker.

When overload occurs on one circuit breaker, forexample breaker 8S, the contact bar will snap upwardly against the pin 92 on thecomrnon trip member. The common trip 'member will thereby be caused to pivot counter-clockwise as viewed in FIGS. 18 and 19, causing the flange 89 to strikev the outer extremity of the pivot pin 68 on the adjacent breaker 84. The contact bar will thereby be 'moved to the right (as viewed in FIG. 3) causing the disengagement of latching surface 69 from the latch 71. The operation is identical when breaker 84 is rstto trip.

In a general manner, while there has been disclosed in the above description,y what is deemed to be the most practical and efiicient embodiment of the invention, it should be well understood that the invention is not limited to such embodiment as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of the present invention as comprehended within the scope of the accompanying claims.

`Having described my invention, I claim:

1. A circuit breaker comprising, a frame, a contact fixed to said frame, a latch movable in said frame and spaced from said fixed contact, a movable contact bar having a contact at one end and a latch engaging surface at the other end thereof, an operator pivotally mounted in said frame and engageable with said contact bar, cam means engaged by said bar to guide said bar and to permit movement of said bar in directions transverse and longitudinal to said bar, said bar having a closed position in which its contact engages said fixed contact and its latch engaging surface engages said latch, and spring means urging said bar toward said fixed contact when said bar is in closed position, said operator beingl engageable with said bar to move said bar longitudinally away from said latch whereby to unlatch said bar and open said contacts.

2. A circuit breaker comprising, a frame, a contact fixed to said frame, a latch movable in said frame and spaced from said fixed contact, a movable contact bar having a contact at one end and a latch engaging surface at the other end thereof, an operator pivotally mounted in said frame and engageable with said contact bar, said bar having a closed position in which its contact engages said fixed contact and its latch engaging surface engages said latch, pivot means intermediate the ends o-f said bar, cam means fixed on said frame and engaged by said pivot means to guide said bar and to permit movement of said bar in directions transverse and longitudinal to said bar, and spring means connected to said bar and urging said bar against said latch and fixed contact, said operator being engageable with said bar to move said bar longitudinally away from said latch whereby to unlatch said bar and open said contacts.

3. A circuit breaker according to claim 2 in which said cam means has a rst surface extending generally in the direction of the force of said spring, and a second surface generally normal to the direction of the force of said spring, said pivot means being slidable first along said first surface and thereafter pivotable about said second surface upon release of said latch.

4. A circuit breaker comprising a frame, a contact xed to said frame, a latch movable in said frame and spaced from said fixed contact, a movable contact bar having a contact at one end and a latch engaging surface at the other end thereof, said bar having a closed position in which its contact engages said fixed contact and its latch engaging surface engages said latch, an operating handle pivoted intermediate its ends to said frame,

. said handle having one end portion engaging a portion of said bar with the extremity of said handle normally extending to the side of said bar portion remote from the pivot of said handle, a spring urging said bar toward said v handle pivot and said fixed contact, and means confining longitudinal movement of said bar within a predetermined range whereby the end portion of said handle toward said lfixed contact will force said bar portion to ride about said extremity of said handle and when said bar portion has passed said extremity said bar will snap its contact into engagement with said fixed contact under the force of said spring.

5. A circuit breaker comprising a frame,A a contact fixed to said frame, a latch movable in said frame and spaced from said fixed contact, a movable contact bar having a contact at one end and a latch engaging surface at the other end thereof, said bar having a closed position-in which its contact engages said fixed contact and its latch engaging surface engages said latch, a pivot pin transversely fixed to said bar intermediate the ends of said bar, cam means on said frame receiving said pin, an'operating handle pivoted intermediate its ends to said frame, said handle having one end portion engaging said pivot pin with the extremity of said handle normally extending to the side of said pin remote from the pivot of said handle, a spring urging said bar toward said handle pivot and said fixed contact, whereby pivoting the end portion of said handle toward said fixed contact will force said pin to ride about said extremity of said handle and when said pin has passed said extremity said bar will snap its contact into engagement with said fixed contact under the force of said spring.

6. A breaker according to claim 5 in which said bar has a longitudinal slot intermediately bridged by said pin, said handle end portion normally projecting through said slot.

7. A breaker according to claim 5 in which said pin projects transversely beyond said bar, said handle end portion being bifurcated and straddling said bar.

8. A circuit breaker comprising a frame, a contact fixed to said frame, a latch movable in said frameand spaced generally horizontally said fixed contact, a generally horizontal, movable contact bar having a contact at one end and a latch engaging surface at the other end thereof, said bar having a closed position in which its contact engages said fixed contact and its latch engaging surface engages said latch, a pivot pin transversely fixed to said bar intermediate the ends of said bar, cam means on said frame receiving said pin, an operating handle pivoted intermediate its ends to said frame, said handle -having one end portion engageable with the side of said pin remote from said contact with the extremity of said` handle normally extending below said pin, a spring urging said bar linearly upwardly toward said handle pivot and said fixed contact and, when said latch is disengaged, rotationally to swing said movable contact away from said fixed contact, whereby pivoting the end portion of said handle toward said fixed contact will force saidbar portion to ride downwardly about said extremity of said handle until said latch engaging surface engages said latch and when said bar portion has passed said extremity said spring will pivot said bar upwardly about said latch and snap the movable contact into engagement with said fixed contact.

9. A circuit breaker comprising a frame, a contact fixed to said frame, a latch movable in said frame and spaced generally horizontally said fixed contact, a generally horizontal, movable contact bar having a contact at one end and a latch engaging surface at the other end thereof, said bar having a closed position in which its contact engages said fixed contact and its latch engaging surface engages said latch, a pivot pin transversely fixed to said bar intermediate the ends of said bar, cam means on said frame receiving said pin, an operating handle pivoted intermediate its ends to said frame, said handle having one end portion engageable with the side of said pin remote from said contact with the extremity of said handle normally extending below said pin, a spring engaging said bar between said pin and latch and urging said bar 1inearly upwardly toward said handle pivot and said fixed contact and, when said latch is disengaged, rotationally to swing said movable contact downwardly away from said fixed contact, and means limiting downward movement of the Contact end of said bar within a predetermined range, whereby pivoting the end portion of said handle toward said fixed contact will force said pin to ride down said extremity of said handle, said limiting means providing a fulcrum about which said bar pivots to bring said latch engaging surface into engagement with said latch and when said pin has passed said extremity said spring will pivot said bar upwardly about said latch and snap the movable contact into engagement with said fixed contact.

10. A circuit breaker comprising, a frame, a contact fixed to said frame, a latch movable in said frame and spaced generally horizontally from said fixed contact, a generally horizontal movable contact bar having a contact at one end and a latch engaging surface at the other end thereof, a pivot pin transversely fixed to said bar intermediate the ends of said bar, a cam surface on said frame engageable by said pin, at least a portion of said cam surface being generally the arc of a circle having a center at said latch, said latch engaging surface being spaced from said pin a distance equal to said radius, whereby said latch engaging surface will be engageable with said latch regardless of the position of said pin on said arc.

11. A circuit breaker comprising a frame, a contact fixed to said frame, a latch movable in said frame and spaced generally horizontally from said fixed contact, a generally horizontal movable contact bar having a contact at one end and a latch engaging surface at the other end thereof, a spring connected to said bar and urging said bar in an upward direction toward said fixed contact, a single operator pivotally mounted in said frame and engaging said bar to force said bar downwardly and away from said fixed contact, means for releasing said bar from engagement with said operator at a predetermined position of said operator to permit said bar to snap upwardly, and cam means to guide said bar and to permit movement of said bar in directions transverse and longitudinal to said bar, said cam means guiding said latch engaging surface into engagement with said latch when said bar reaches its predetermined position.

l2. A two pole circuit breaker combination comprising; two circuit breakers disposed in spaced side by side relation; each said circuit breaker having a casing, a contact fixed to said casing, a movable contact bar having a contact engageable with said fixed contact, a spring means connected to said contact bar for moving said contact bar to a position in which said contacts are disengaged, latch means for maintaining said contacts in engagement; a common trip member movably mounted between said breakers; said trip mem-ber being engageable by one of said contact bars for movement when said spring means moves said contact bar to disengage said contacts, the other of said contact bars being engageable by said trip member when moved by said one contact bar to effect unlatching of said other bar.

13. A two pole circuit breaker combination comprising; two circuit breakers disposed in spaced side by side relation; each said circuit breaker having a casing, a contact fixed to said casing, a movable contact bar having a contact engageable with said fixed contact, spring means connected to said contact bar for moving said contact bar to a position in which said contacts are disengaged, a current responsive member mounted in said casing, cooperating latch elements on said current responsive member and said contact bar for maintaining said contacts in engagement; a common trip member movably mounted between said breakers; said trip member being engageable by one of said contact bars for movement when said contact bar moves upon tripping, the contact bar of the other circuit breaker being engageable by said trip member to effect unlatching.

14. A circuit breaker comprising, a frame, a contact fixed to said fra-me, a current responsive latch member mounted in sa-id fra-me to move toward said fixed contact for unlatoliing, a movable contact bar having a contact at one end and a latch portion at the other end thereof for latched engagement with said current responsive latch member when said contacts are closed, said latch portion comprising an L-shaped hook having a transverse surface engageable with `said latch member on the one side of said latch member remote from said fixed contact, and means for bodily moving said contact bar away from said fixed contact to efiect disengagement of said latch portion from said latch member.

l5. A multi-pole circuit breaker combination comprising at least two circuit breakers; each said circuit breaker comprising a frame, a contact fixed to said frame, a current responsive latch member mounted in said frame to move in a first direction for unlatching, a movable contact bar having a contact at one end and a latch portion at the other end thereof for latched engagement with said current responsive latch member when said contacts are closed, said latch portion being disengageable from said latch member by Ibodily moving said contact bar in a second direction opposite to said first direction; and a common trip member operable by a tripped circuit breaker and engageable with the contact bar of an adjacent circuit breaker to move said contact bar in said second direction.

References Cited in the file of this patent UNITED STATES PATENTS UNITED "STATE s PATENT @FFME CERTIFICATE 0F CGRRECTION Paten?, NQ@ lgi January 23V i962 William Middendmvf It is `lflergisby certified that error appears in the abova numbered. patent requiring co'rection and that the said Letters Faisant should read as corrected below.

(301mm 7V line 64, @figer ni/whereby imserfi am pivtinq mg column 8U line 48V after horiznfgalym a imm 95 cmlumn 9U line 33V smaike @am amg iin@ 439 beim@ mbar insert, Contact me; column "iOI line 1&7 s'wik@ @uit miem Signed and sealed Ehi@ 5th day June lw (SEAL) Attest:

lERNEST w swIDER MWD-L MDD Attesting Ufficer l Commissioner nf Patents UNITEUSTATES PATENT ermee CERTIFIGATEv 0F CQRRECHGN Patent qlq 231, i952 Wam Ht vftddeim 1t is hereby certified that error appears in the above numbered pat ent requiring correction and that the said Lettere Patent should read as corrected below.

Column *L line 64,1 after reby" Meert, m Celular. line 48V after Miterrally" Column 9V line 33V am; time @5E/ bezere insert Contact =g column, 0g .e v @ttt enema Signed and Sealed this 5th @if tmp i952@ (SEAL) Attest:

ERNEST wo swlDER MWD-L MDD Attesting Officer Commissioner ef Patents 

